A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames. Issue 5 (3rd September 2018)

• Record Type: Journal Article
• Authors: Chen, Zhi X.; Doan, N. Anh Khoa; Ruan, Shaohong; Langella, Ivan; Swaminathan, N.
• Is Part Of: Combustion theory and modelling. Volume 22:Issue 5(2018)
• Page Start: 862
• Page End: 882
• Publication Date: 2018-09-03
• Subjects: DNS -- partially premixed flame -- subgrid correlation -- LES -- copula; Combustion -- Mathematical models -- Periodicals; 541.361
• DOI: 10.1080/13647830.2018.1459862
• Languages: English
• ISSNs: 1364-7830

Abstract

Abstract : Subgrid correlation of mixture fraction, Z, and progress variable, c, is investigated using direct numerical dimulation (DNS) data of a hydrogen lifted jet flame. Joint subgrid behaviour of these two scalars are obtained using a Gaussian-type filter for a broad range of filter sizes. A joint probability density function (JPDF) constructed using single-snapshot DNS data is compared qualitatively with that computed using two independent β-PDFs and a copula method. Strong negative correlation observed at different streamwise locations in the flame is captured well by the copula method. The subgrid contribution to the Z – c correlation becomes important if the filter is of the size of the laminar flame thickness or larger. A priori assessment for the filtered reaction rate using the flamelet approach with independent β-PDFs and correlated JPDF is then performed. Comparison with the DNS data shows that both models provide reasonably good results for a range of filter sizes. However, the reaction rate computed using copula JPDF is found to have a better agreement with the DNS data for large filter sizes because the subgrid Z – c correlation effect is included.